Process of synthesizing hydrocarbons



Patented Dec. 25,1951

UNITED STATES PATENT 2,579,663 OF CE-i .HYDROCARBONS William I. cnbm and Charles w. Montgomery, Oakmont, Pa assignors to Gulf Research &

Development Company, Pittsburgh, Pa., a corporation of Delaware No Application December 15, 1948,

- I Serial No. 55,527

This invention relates to a process for syn j I (c1. zoo-449.6)

thesizing hydrocarbons; more particularly the invention relates to a process for synthesinng normally liquid hydrocarbons from carbon monoxide and steam.

The reaction between carbon monoxide and steam has been employed in the past for the reaction has" been carried out in the presence of catalysts, at

manufacture of hydrogen.

a temperature in the neighborhood of 900 to 950 F. and at substantially atmospheric pressures. The products of reaction consist of hydrogen and carbon dioxide, together with unconverted steam and carbon monoxide.

We have now discovered that carbon monoxide and steam can so as to produce among the products of the reaction an important yield of normally liquid hydrocarbons; i.e., hydrocarbons that are liquid at atmospheric temperature and pressure conditions. Thus, we have found that such liquid hydrocarbons can be produced by reacting carbon monoxide andsteam in the presence of a solid catalyst and at a temperature of about 400 to about, 700'- I". and a pressure of above 100 pounds per square inch. This process is advantageous in that the raw materials for the process are relatively inexpensive and the products include not'only the valuable liquid hydrocarbons, but also a proportion of hydrogen which is available for use in hydrogenation processes such as the Fischer- Tropsch synthesis processinvolving the reaction between carbon monoxide and hydrogen;

In carrying out the 'process of the invention, .the charge mixture of carbon monoxide and steam is preferably prepared before being brought 'should be controlled by the use of' suitable heat exchange means such as cooling coils, tubes and reactor jackets or by high recycle ratios The process may also be-carried out by using the catalyst in fluidized state mby passing the catalyst through the reactor as a moving bed. In these cases the temperature control may he efl'ected by the use of heat exchange means or by using high catalyst circulation rates or both. We have found that the production of hydrocarbons is most. efficient when the temperature is maintainedbetween about 500 and about 600-.F., and preferably between about 550 and .about 600' F. r v a The reaction pressure is an important feature of the process. We have found that when reacting carbon monoxide and steam at atmospheric pressure normally liquid hydrocarbonsare not obtained eyen though all of the other conditions of the process are optimum. To produce reasonable yields of hydrocarbons, the pressure should be maintained above 100' pounds per square'inch, and preferably between about 150 and about 300 pounds per square inch. Although higher pressures do not appear to have an ,ad-

' verse effect, the use of such pressures intro in contact with the catalyst. The ratio of carbon monoxide to steam in the charge mixture hasfan important effect upon the results achieved. While the reaction produces-hydrocarbons when using carbon monoxide and steam in mol ratios from about 0.5:1 to about 3:1, we have found that the most effective results are obtained when using ratios'from about 121,10 about 2: 1'. When a lesser amount of carbon monoxide is used, the yield of hydrocarbons falls rapidly. a d when a greater quantity of this reactant is included in the charge mixture, carbon is produced which is deposited in the pores of the catalyst, resulting in the rapid destruction of the physical form of the catalyst. This physi'calfdecomposition of the catalyst causes, in a fixed bed operation, rapid increase in pressure drop across the catalyst bed, and in operations. where the catalyst is caused to move through the reaction chambeg, the production of catalyst lines which are the --r:. 4

duces operating diiliculties and, therefore, pressures above about 600 pounds per square inch are undesirable. I

Any suitable solid catalyst may be employed in the'process. We have; found that the reacidon is especially sensitive to the specific nature I or the catalyst. Thus, in accordance with a preferred embodiment of the invention, a mix-.

ture of carbon monoxide and steam is contacted, under the conditions described above, with an --iron catalyst'which is from about to about 1 bons are obtained.

"40 to about 80 per cent reduced, and is preferably about 50 to about '75 per cent reduced, from the cobalt oxide, is an effective catalyst for this reaction. The particular efiectiveness of cata- 3 lysts of these types for the reaction is somewhat surprising because related catalysts, such as a completely oxidized iron catalyst-or a completely reduced cobalt catalyst, have been found, under the conditions employed in the research work leading to the development of this inven-- tion, to produce at best only very small yields of the desired hydrocarbons.

Accordingly, while the invention includes in its broader aspects the use of any suitable solid catalyst, particularly a suitable synthesis catalyst, it will be understood that these catalysts will vary greatly in respect of their effectiveness in the present process depending upon the degree of oxidation or reduction of the catalyst. In referring to synthesis catalysts we intend to indicate the catalysts that have been employed or proposed for use in thesyn'thesis of hydrocarbons by the Fiseher-Tropsch process, preferably catalysts comprising metals of group VIII of the periodic table; especially the iron group metals,

iron, cobalt, and nickel. The catalysts may he supported on any suitable supports such as diatomaceous earth, silica gel, alumina, activated plays, bauxite, activated carbon and kieselguhr, and they may contain promoters, examples of which are alumina. potassium oxide, magnesium oxide, calcium oxide, copper and thoria.

In order that the invention may be understood more fully reference should be had. to the followingspecific examples.

EXAMPLE! H .A series of reactions were carried out using an iron catalyst in several stages of reduction. This catalyst was a pelleted precipitated iron .oxide which analysis'indicated was essentially Fez0a although it contained traces of other metals. To prepare this catalyst for use as a reduced oxide, it was first dried at 750 F. and then was reduced by passing hydrogen over it at a pressure of about one atmosphere while maintaining temperatures of about 750 F. The percentage reduction was determined by using the ratio between the water formed in the reduction of the catalyst and the theoretical amount of water that would be produced by complete reduction. As' an example, complete reduction of 100 grams of dry FezOa will produce 33.8 grams of water. If the reduction is carried out in the above manner so as to produce 22 grams of water, then the percentage reduction is 22/33.8 100 or per cent. This catalyst is referred to as a 65 per cent reduced iron catalyst;

As shown in the following Table I. several iron catalysts were used in which the conditions of operation were varied as shown in the table.

the catalyst bed fairly constant throughout the,

run. The products of the reaction were col.- lected and analyzed as shown.

' Table I BunNo...--.......--. 1 2 3 4 8 Per Cent Reduction of a yst sac 10 no o Moi Ratio CO/HaO of am... -17: (1.99 msus 2.0,, 8pm Velocity 01..

ehargeatB.T.P ol. Catalyst/Hour) 483 4s: mm as ms 575' 515 57s no no o as can 01.: .u 30.9. 4.3 a2 4.4 86.1 no 2&1 19.1 17.6 as see as so as Trace as 01+ as aaaa m M Yield-lbs. liquid hydrocarbonsparMCF CO. 2.82 "12.0 2.3. None None although all of the other conditions were substantially optimum, the use of atmospheric pressure resulted in an-operation in-which no liquid hydrocarbons were formed. Also, comparison of runs Nos. 1 and 4 will show the relation between the, effectiveness of a substantially. completely reduced iron catalyst and an unreduced or oxidizedironcatalyst In this example the catalyst employed was a familiar type of synthesis catalyst consisting of cobalt impregnated 'on kieselguhr and promoted with thoria having the composition by weight of 45.9 per cent cobalt oxide, 8.2 per cent 'thoria, and 45.9 per cent kieselguhr. As obtained the catalyst was in the substantially completely oxidized state'. To'prepare reduced or partially reduced catalysts, the catalystwas treated by passing hydrogen over it at-a temperature of about 650 to about 750 F. and at a pressure of 150 pounds per' square inch gauge and-a space velocity of 400 in some and at atmospheric pressure and a space velocity of 400'0'in other runs. The per cent reduction of each catalyst was determined as described in Example;

The following Table 11 shows the results obtained using various cobalt catalysts prepared by reduction with hydrogen .as describedi'when reacting carbon monoxideand described inExample-I. 7

z'ableiz. BunNoi 11 12 13 14*" J15 '16 g 'Per Cent Reductionofcamlyst. 55.5 73.3 10.6 93.8 no $1.8 Moi Ratio CO/"HaO oicharge---- 1.43 1.0 0.50 1.0 1.0 -..1.84,

- Space Velocity OL-charge at 8. '1. PJ'Vol. atalyst/Hour)- 434 44 833 500 :500 Average-Reactor Temperature "F $75 575 575 "all 576 Pressure-pounds per sq. inch I 50.0 63.0 38.2 "70.3 8.8 41.5 21.0 4.3 35.2 0.4 AL! T 126 11.0 10.0 73! 8.8 3 6.8 11.4 4.0 17.8 0.0 Cri- 2-1 23 0.0 2.2 1.0 Yield-lbs. liuuld hydrocarbons perMCF CO 1.0 0.8 Trace Trace None 0.48

It will be seen from this table, Run No. 5, that apropos It will be seen from the data given in Table II, that while normally liquid hydrocarbons were obtained when using a partially reduced catalyst in runs 11 and 13, at best only a trace of such hydrocarbons was obtained when using either substantially completely oxidized or substantially completely reduced catalyst. The data also show that when using a cobalt catalyst, the best results are obtained when the carbon monoxide/steam ratio is between 1.0 and 1.5.

The results obtained in the foregoing runs and other runs carried out in the research work in connection with the invention hav indicated that the space velocity need not be restricted to narrow limits. In general, we prefer to employ space velocities of fresh feed within the range of about 200 to about 800 but both lower and higher fresh feed space velocities may be used by appropriate adjustment of the other conditions of the process.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may

be made without departing from the spirit and' scope thereof, but only such limitations should be imposed'as are indicated in the appended claims.

Weclaim:

1. A process for the production of normally liquid hydrocarbons which comprises contacting a mixture in which the reactants consist of carbon monoxide and steam in a mol ratio of carbon monoxide to steam or about 2:1 with an iron catalyst substantially completely .reduced from the oxide at a pressure of about 150 to about 300 pounds per square inch and at an elevated conversion temperature from about 550- to about 600 F., and-recovering normally liquid hydrocarbons from the reaction products.

2. A process for the production of normally monoxide to steam ofabout 1:1 to about 2:1

with a catalyst selected from the group consisting of an iron catalyst about 50 to about 100 per cent reduced from the oxide and a cobalt catalyst about to about 80 per cent reduced from the oxide, at a pressure of about 100 to about 600 pounds per square inch, and at an elevated conversion temperature from about 500 to about 600 R. and recovering normally liquid hydrocarbons from the resulting reaction prodliCtS,

4.Aprocess accordingtoclaim 3 inwhich said catalyst is an iron catalyst about toabout 100 per cent reduced from the oxide.-

flle of this patent:-

liquid hydrocarbons which comprises contacting a mixture in which the reactants-consist of carbon monoxide'and steam in a i'n'ol'ratiii of carbon monoxide to steam of about 1:1 to about 1.5:1

5. A process in accordance-with claim 3 in which said catalyst is a cobalt catalyst about 40 to about per cent reduced from the oxide.

WIILIAM I. GILBERT.

' 'CHARLES W. MONTGOMERY.

' ameness The following references are of record in the .UNITEDBTATES ra'rafi'rs I Number Name Date 2,213,415 Slatineanu 8ept. 3. 1940 2,257,293 Dreyfus pt a0, 1941 Fischer: Conversion to: Coal in bi'Q L July 18, 1025, pages 21 -319. a 1 

3. A PROCESS FOR THE PRODUCTION OF NORMALLY LIQUID HYDROCARBONS WHICH COMPRISES CONTACTING A MIXTURE IN WHICH THE REACTANTS CONSIST OF CARBON MONOXIDE AND STEAM IN A MOL RATIO OF CARBON MONOXIDE TO STEAM OF ABOUT 1:1 TO ABOUT 2:1 WITH A CATALYST SELECTED FROM THE GROUP CONSISTING OF AN IRON CATALYST ABOUT 50 TO ABOUT 100 PER CENT REDUCED FROM THE OXIDE AND A COBALT CATALYST ABOUT 40 TO ABOUT 80 PER CENT REDUCED FROM THE OXIDE, AT A PRESSURE OF ABOUT 100 TO ABOUT 600 POUNDS PER SQUARE INCH, AND AT AN ELEVATED CONVERSION TEMPERATURE FROM ABOUT 500* TO ABOUT 600* F., AND RECOVERING NORMALLY LIQUID HYDROCARBONS FROM THE RESULTING REACTION PRODUCTS. 